Electron discharge device



June 25, 1946. G. P. CHEVIGNY ET AL 2,402,500

ELECTRON DISCHARGE DEVICE Filed Jan. 22, 1942 I I V y V a0 75 76": g gg e? no.3. 77 70 74'.

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Patented June 25, 1946 ELECTRON DISCHARGE DEVICE Georges Paul Chevigny, Kew Gardens, and Emile Labin, New York, N. Y., assignors to Federal Telephone and Radio Corporation, a corporation of Delaware Application January 22, 1942, Serial No. 427,728

4 Claims. 1

This invention relates to electron discharge devices and circuits, and more particularly to such apparatus adapted to operate at ultra high frequencies. It has for its object to improve the operating performance, and increase the frequency and the power output at which such devices may be made to operate effectively. A related object is to provide a simple compact construction, by which an efiicient operation is obtained.

There have heretofore been provided vacuum tubes having resonant cavity type circuits arranged to establish ultra high frequency resonance. To enable such tubes to operate effectively, the size of the electrodes should be made small in order that a substantial transfer of energy of the ultra high frequency may be made effective over the electrode areas. Furthermore, it is desired that the electrical impedance of the elements coupling the resonant circuits with the tube electrodes should be made small in order to reduce the power loss across them.

In accordance with this invention there is provided a compact symmetrical arrangement of the component parts of the tube and cavity circuits,

which reduces the effective size of the electrodes to half their actual size, and thereby permits a high energy output at a very high frequency. A feature is an arrangement of the cavities symmetrically with respect to the central section of the electrodes so that the tube operates as two tubes, one on either side of the central section. Another feature is the arrangement of a coupling capacity within the vacuum of the tube, through which the cavity is coupled with the corresponding tube electrode, thus facilitating the provision ofa large coupling capacity.

The invention will be understood from the following detailed description taken in connection with the accompanying drawing, of which Fig. 1 shows in longitudinal section, a vacuum tube construction embodying the invention;

i Fig.2 shows in section, a modified construction according to the invention; and

Fig. 3 shows a modification of the arrangement shown in Fig. 2.

Fig. 1 shows a device which is in effect a double tube. It comprises a pair of cathodes l and Illa, in a well-known form of filaments displaced longitudinally from each other along the longitudinal axis and supported on filament leads H, I2 and I3. The lead I l is connected at the filament midpoint, sealed through insulating dish l4, forming part of the wall of the evacuated vessel. There is placed concentrically around the longitudinally spaced cathodes ID and 10a, a cylindrical grid electrode l5, which may be formed in a wellknown manner to act as a control grid, and having end portions 16 and H which may be imperforate conducting cylinders. The grid itself may be a helical wire winding or some equivalent construction such as spaced rods. The grid may be supported in a practical manner; and in Fig. 1, it is shown held by the collar l8 around the midsection, supported by the rigid grid lead l9, which passes through the sealing glass 20 having the annular portion 2|, which in turn is sealed to a cylinder 22, which may be of metal, protruding outwardly from the side of the cylindrical anode 23. This anode is placed concentrically around the grid electrode, and may be supported in a practical way such as between end flanges 24 and 25, which are sealed to respective insulating cylinders 26 and 21, ordinarily of glass, forming part of the evacuated vessel wall and extending beyond the respective ends of the anode. This concentric anode construction is fastened to the insulating dish 14 by means of a conducting collar 28, having flanges 29 and 3|], which are sealed respectively to cylinder 21 and dish M.

The tube is closed at the opposite end by the metallic dome-shaped member 3| attached to a conducting collar 32, which is sealed to the glass cylinder 26 by means of flange 33.

For the purpose of tuning the anode-grid circuit, there are provided two tank circuits in the form of resonant cavities 34 and 35, in the form of bodies of revolution; coaxially and symmetrically located with respect to the electrodes. Each of these cavities comprises an outer wall, 36 and 36a respectively, flaring and extending concentrically from the ends of the anode, and inner walls 31 and 31a respectively, extending concentrically from the collars 32 and 28 respectively, so that the outer and inner walls of the cavities form concentric lines, as shown. Annular plungers 38 and 38a may be placed in the annular space of each concentric line to tune it. These plungers are preferably made movable endwise as indicated by their handles, so as to afford a tuning adjustment. Y

For the purpose of coupling the inner walls 31 and 31a with the respective grid ends to form the anode-grid circuits, there are attached to the collars 32 and 28 respectively, conducting cylinders 39 and 39a which extend inwardly and close to the respective cylinders l6 and I! at the ends of-the grid element so that capacity forms between cyllnders l6 and 39, and between 11 and filaments. The walls 4! and 3.170: are capacitively coupled by a coupling condenser formed by annular disc 52 in contact with cylinder 37a, and an annular disc E3 in contact with cylinder fill. These discs may both be movable in an endwise direction, as indicated, so that the capacity therebetween and the resonance of the grid-filament circuit can be adjusted.

By its symmetrical construction, the device'may be made to operate as two tubes, the two parts being divided at the mid-section line 45 between the filaments In and Illa. Thecathode Ill, to gether with its corresponding half of the grid and anode, and the resonant tank circuit 34, operate as one tube, and the other cathode 15a together with its grid and anode and the tank circuit 35, simultaneously operates asanother tube.

The-device maybe operated in the usual 'manner, the required filament voltage being connected to filament leads I2 and 13, a suitable control grid voltage to lead 19, and a suitable anode voltage to anode 23. It may be used as an amplifier, or if desired, as an oscillator by providing suflioient feed-back from the anode circuit to the grid-filament circuit in a wellknown -manner. Such feed-back could be provided, forexample, by connecting a concentric line between cavities 34 and 35 if there is not already sufficientcoupling between the-electrodes within the tube. Energy can be taken from the tube in a well-known .manner such as by placing asuitableenergy pick-up device within a cavity. Such an arrangement itshown as the conductingloop 46 connectedv inside cavity-34 andbrought out through concentric tubing t1. 7

Fig.2 illustrates another form of tube which likewise acts as a .double tubealthoughhaving a cathode built asasingle unit 50. .This issurrounded by the-concentricgrid and anode 52 in a similarmanner'tothat illustrated in Fig. 1.

It; is :provided with .a single symmetrical tank extending fromone' end of the tube to another. This'is formed by the enveloping conducting .wall 53, placed concentrically, around the tube and flaring from the terminal collar. .54 atone end, and from the metallic tube sealing .member 55 at "the other end. Coupling capacity between the tank and the grid is the metalcylinder 56, which is .re-entrantly extended within the cylinder 58 at the end of the grid. As the cylinder 56 forms part of the wall of the evacuated vessel, this coupling capacity between wall 55 and member 58 has the advantage ofbeing within the vacuum. This capacity 56, 53 may be usediorfacility of construction and assembly; for the grid member 5| may be in serted into the tube from the right, and the circuit from the left end of the, grid to the cavity will be completed through the capacity. This arrangement has the advantageQof permitting relative movement between member 58 and 55, as when expansion occurs through heating. If convenient, the members 56 and 58 might be connected together directly, if provision be, made for taking care of the thermal expansion of the grid.

There is provided a grid-cathode circuit by means of .coaxial cylinders 59 and60, thecylinder '59-, being attached to collar. 54, .andhylinder 6Z0 provided bymeans of 3,

' tively with the coaxial line walls 59 and 60.

a conducting rod 52a may be attached to the being attached to the cathode mid-lead at Bl. Cylinders 59 and 60 form a coaxial line, and it may be tuned in a manner somewhat similar to that in Fig. 1 by means of the annular discs 62 and 63 located between, and connected respec- These lines 62 and t3 may be arranged to move endwise by suitable-manipulating members 64 and 65,asshown.

In order to supply anode voltage to anode 52,

anode and led out through a hole 53b in the cavity wall. '53, such that the rod is insulated from Wall-53.

Fin 136 for cooling may be built to extend radiallyfrom theanode 52. If it is desired to make provision'for air cooling, there may be provided air spaces 67 leading into the tank, and through which air may pass over the fins.

In the embodiment of .Fig. 2, the operation is like that of a double tube, beingvery similar .to the operation of the embodiment shown in Fig. 1. Although there is "onlya single cathode inFig. 2, the eflect of the symmetrical construction of the electrodes and tank is to cause the half of the apparatus at the right of the center section 68 to operate as-one device, and the other half as another device in parallel, and the end of each tank is effectively at the center section by reason of the symmetrical construction of the elements both concentrically and in a longitudnal direction.

. Fig. 3 illustrates 'a modification of the arrangement shown in Fig. .2, :in which a conducting lead 10 is capacitively coupled to the filament midpoint lead H by means of a capacity'couplin'g provided by a cylinder 12 attached to the lead it and surrounding member II. To .permit lead 70 to be brought outside the tube, the end wall of the tube is formed by the glass dish 13, which is sealed to the metallic section 74 of the wall of the vacuum tube. .Member 1.4 has formed integralwith it, ,a'collar115 to which is attached the cylinder 16 which forms with the end 5.8 :of :the grid, a capacity coupling asinthe case of-Eig. 2. The conducting lead 'lflis'extendedforsa distance coaxially beyond theend of the tube; and there is attached to its end, the closed end ofza'cylinder .11 coaxially positionedwith respect to the tube, and extending endwise of it. -There is placed concentrically around the cylinder 17 another cylinder 18 attached to the collarl5, so'that-cylinders l1 and 18 form'a coaxial line. ,There are placed in this line movable'discs 19 :and 18.0,, .similar to discs .62 and 63in Fi .2. Thesediscs are movable endwise by their regulating *rods so as to tune the line and also form capacity therebetween.

.It will be understoodthat the right end of the tube in Fig.3'can be made as theright end of'the tube in Fig. -2. With this construction, there is provideda tube which notonly has asymmetrical anode-grid resonant circuit, but also has symmetrical cathode-grid circuits, each of which is tunable. I I a I J I The use of cylinders 12 around the filament mid-leads ll, provides suflicient'capacity at the ultra h frequencies to make a relatively :low impedance couplin from lead H to lead 'll]; ;It

"has the advantage ofproviding simplicity .of 'asy- .the rods 10 and .H :might be made a single continuousirod'passing throughiboth ends of the tubc if suitable provision be made for taking care of expansion and contraction of the rod durin changes of temperature.

As a result of the eifective operation being that of two tubes in parallel in the construction shown, the tube electrodes act electrically as though they were only half their real length; and since their effective length is thus reduced it is possible to operate the tube at a correspondingly higher frequency than otherwise, and still obtain a relatively high degree of energy output from the tube. The constructions, enabling the anode circuitgrid coupling capacity to be placed within the vacuum of the tube, results in a further increase of output by reducing the voltage loss across this capacity and reducing the tendency toward sparking between the capacity armatures at high voltages, which occurs less readily in vacuum than in air; and this enables the condenser plates to be brought closer together. The resultant increase of capacity has the desired effect of reducing the voltage fall across it.

What is claimed is:

1. An evacuated ultra-high frequency electron discharge device comprising symmetrically mounted cathode, grid and anode electrodes in which the grid surrounds the cathode and the anode surrounds the grid, an envelope surrounding said cathode and grid electrodes, said anode forming part of said envelope, a cylindrical member extending in said envelope and forming a conpling capacity with the grid, and cavity resonator means effectively connected to the anode and said member and symmetrically mounted both coaxially and longitudinally with respect to the electrodes.

2. An ultra high frequency electron discharge device comprising an evacuated vessel, a pair of centrally located cathodes within said vessel, a control electrode mounted concentrically around the cathode, an anode mounted concentrically around the control electrode and forming part of the vessel, and a pair of coaxial cavity walls concentrically mounted both coaxially and longitudinally with respect to the electrodes, one of said walls extending through each end of the vessel and connected with the grid through a capacity coupling within the vacuum.

3. An ultra high frequency electron discharge device comprising an evacuated vessel, a centrally located cathode within said vessel, a control electrode concentrically around the cathode, an anode concentrically around the control electrode and forming part of the vessel, a pair of concentric cavity walls, one being connected with one end of the anode and the other with the other end of the anode, said Walls extending outside the vessel in the direction of the respective ends of the Vessel, and a second pair of concentric cavity walls extending outside the vessel and mounted Within the respective ones of the first pair of cavity walls, and means capacitively coupling said cavity walls with the respective ends of the control electrode through capacity members Within the vessel.

4. An electron discharge device adapted for ultra high frequency operation, comprising an evacuated vessel, a cathode and a control grid within the vessel, said cathode being concentrically mounted within the vessel, said grid concentrically surrounding the cathode, and an anode concentrically surrounding the grid and forming part of the wall of the evacuated vessel, a cavity resonator connected to the anode, and a cylinder extending within the vessel and forming a coupling capacity between the grid and the cavity resonator.

GEORGES PAUL CHEVIGNY. EMILE LABIN. 

